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Liver Dissection Lesson

Liver Dissection Lesson

Welcome to our Liver Dissection Lesson aimed at GCSE students.

We have a liver dissection video demonstrating the methodology of the classroom dissection of a pig’s liver.  We have included a lesson plan and risk assessments that can be downloaded or simply reviewed here.

We hope to guide pupils through discovering as much as they can from the liver!

Aim: To explain how the structure of the liver is related to its function including the use of enzymes.

GCSE Biology

Methodology:

  • Place liver in dissection tray.
  • Cut a section of the slightly smaller left lobe, to examine the internal structure of the liver.
  • The portal vein and the hepatic artery should be identifiable, by the difference in their appearance; The artery should have a thick rubbery wall, and the vein should have a much thinner wall.
  • Remove a section of liver tissue and blend in a pestle and mortar.
  • Put one drop of the blended liver on a dropping tile.
  • Add one drop of hydrogen peroxide. You should see a lot of oxygen bubbles demonstrating the liver enzyme catalase is working to start the chemical reaction that breaks down the hydrogen peroxide that would be harmful to the body into less dangerous compounds.
  • To test the effect of temperature, put one teaspoon of the blended liver into a microwave-safe bowl. Cover the bowl and microwave it on high for 20 seconds. Add hydrogen peroxide as before.
  • Try experimenting with other conditions. For example, to test the effect of an acid on the liver enzyme, put one teaspoon of the blended liver in a bowl and mix it well with one teaspoon vinegar. Or a base by adding baking soda.
  • As a teacher demonstration, a piece of tissue can be added to conical flask with hydrogen peroxide and a ‘glowing splint’ test can be performed on the gas bubbles to demonstrate the gas being oxygen (a glowing but blown out splint should re-light).

 

Teaching Notes:

The liver is important for cleaning up any potentially dangerous substances consumed. Within your liver, as within every tissue in the body, many enzyme chemical reactions occur.

The liver uses specialised enzymes to break down toxic substances. These enzymes need certain environments to be effective, whereas others can prevent it from working at all.

Enzymes such as catalase are large proteins that speed up the rate of a chemical reaction by acting as a catalyst.

Catalase is an enzyme in the liver that breaks down harmful hydrogen peroxide into oxygen and water. When this reaction occurs, oxygen gas bubbles escape and create foam.

Experiment with different enzyme conditions and discuss:

Did more, less or about the same amount of bubbles form?

Did they form more slowly, more quickly or at about the same rate?

Based on your observations, under which condition(s) does it look like the enzyme works best? Why do you think this is so?

Observations to point out:

  • The liver is made up of 4 distinct lobes, with the right and left lobes being the largest, and the right lobe is larger than the left.
  • If you cut a section of the left lobe, you can examine the internal structure of the liver.
  • The portal vein and the hepatic artery should be identifiable, by the difference
  • in their appearance; The artery should have a thick rubbery wall, and the vein should have a much thinner wall.
  • Samples For Schools Liver
  • Dissection tray
  • Scalpel
  • Scissors
  • Mounting needle
  • Ruler or calipers with mm divisions
  • Paper towel
  • Pestle and Mortar
  • Hydrogen Peroxide (for enzyme reaction)

AQA: Topic 4.2.2.1 and 4.2.2.6 and 4.5.3.3

Students should be able to describe the nature of enzyme molecules and relate their activity to temperature and pH changes.

Bile is made in the liver and stored in the gall bladder. It is alkaline to neutralise hydrochloric acid from the stomach. It also emulsifies fat
to form small droplets which increases the surface area. The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.

The effect of alcohol on the liver and brain function.

Edexcel: Topic 5.3.2 and 7.22

Explain how Describe that many non-communicable human diseases are caused by the interaction of a number of factors, including cardiovascular diseases, many forms of cancer, some lung and liver diseases and diseases influenced by nutrition diseases

State that urea is produced from the breakdown of excess amino acids in the liver.

Eduqas: Topic 4.2 and 1.3

Learners should be able to explain the role of adrenaline in the body. Description should be limited to the effects of adrenaline on the heart, breathing and muscles. Adrenaline is converted into a less active compound by the liver.

Explain that chemical reactions in cells are controlled by enzymes.

OCR 21st Century: Topic B3.1

Practical – rates of enzyme-controlled reactions.

OCR Gateway: Topic B6.3 B1.2g

Students should recall that many non-communicable human diseases are caused by the interaction on of a number of factors – liver cirrhosis.

Explain the mechanism of enzyme action.